The aim of this research is to formulate expirical laws relating hormonal conditions during prenatal and postnatal periods to the development of male and female reproductive processes. By varying the amount of circulating steroids present during specific perinatal ages, the degree of homotypical and heterotypical reproductive capacity can be determined for each genetic sex. These manipulations can also cause and regulate the time of occurrence of suppression of female physiological and behavioral processes. The time course and nature of the induced dysfunctions in ovulation, hypothalamic-hypophyseal regulation of gonadotropins, sexual organ morphology, and behavioral receptivity are being investigated in females. Conditions leading to comparable earlier-than-normal degenerative changes in male neural, somatic, and behavioral processes will be identified. Decline in the expression of heterotypical sexual patterns resulting from these manipulations will also be studied. Particular emphasis will be placed on identifying limbic and hypothalamic areas exhibiting changes in functional characteristics which correlate with the time course and nature of modifications occurring in endocrine and behavioral processes. The relationship of these areas to phasic and tonic release of pituitary hormones and to the mediation of normal and modified male and female behavior will be described. An attempt will be made to relate the consequences of experimentally induced, timed degenerative changes in physiology and behavior with those appearing as a result of natural aging. Variables will be introduced which could retard or accelerate these changes. The hypothesis that ovarian secretions potentiate "aging" processes will be examined. In general, the role of ovarian secretions in producing relatively permanent effects in reproductive capacity in each sex is being re-evaluated.